Bicycle Sprocket Assembly With Variable Tooth Spacing for Smooth Shifting

Solution Overview

Problem

Existing bicycle sprocket designs face challenges in reducing weight without compromising structural strength or obstructing gearshifting, particularly during initial gear changes where the chain is inclined and subjected to lateral forces.

Innovation Solution

The design incorporates a sprocket with a combination of teeth and spaces, where at least two consecutive teeth engage the chain during gearshifting, distributing the load and reducing the risk of chain obstruction, and includes spurs that replace removed teeth to maintain engagement without penalizing gearshifting, allowing for weight reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If teeth are removed from the sprocket to reduce weight, then the sprocket weight decreases, but the structural strength and gearshifting performance deteriorate

Engineering Contradiction:

Improvesprocket weightVSAvoidstructural strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The patent applies local quality by creating spaces of different sizes at different locations on the sprocket. First spaces are created between the first gearshifting tooth and second tooth to facilitate chain movement during gearshifting, while second spaces are created downstream to reduce weight. This localized modification allows weight reduction in non-critical areas while preserving structural integrity and gearshifting function in critical areas.

Inventive Principle:

Principle #3Local quality

2Weight of moving object

If teeth are removed from the sprocket to reduce weight, then the sprocket weight decreases, but the gearshifting fluidity deteriorates

Engineering Contradiction:

Improvesprocket weightVSAvoidgearshifting fluidity

Core Design Contradiction:

Weight of moving objectVSEase of operation

Solution Approach 1:

The patent applies local quality by creating spaces of different sizes at different locations on the sprocket. First spaces are created between the first gearshifting tooth and second tooth to facilitate chain movement during gearshifting, while second spaces are created downstream to reduce weight. This localized modification allows weight reduction in non-critical areas while preserving structural integrity and gearshifting function in critical areas.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If the number of sprockets is increased to provide more gear ratios, then the gear ratio options increase, but the sprocket assembly weight increases

Engineering Contradiction:

Improvegear ratio optionsVSAvoidsprocket assembly weight

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The patent applies discarding and recovering by selectively removing certain teeth (creating spaces) from the sprocket to reduce weight. The removed teeth are those located downstream from the gearshifting area, where their absence does not affect the gearshifting function. This allows the sprocket to maintain its weight-reducing potential while preserving the necessary functional teeth for chain engagement and gearshifting.

Inventive Principle:

Principle #34Discarding and recovering

Data Source

PatentUS11492077B2Bicycle sprocket and sprocket assembly comprising such a sprocket

Publication Date: 2022.11.08 CAMPAGNOLO SRL

AI summary

A bicycle sprocket has a plurality of teeth arranged one after the other along a circumferential direction and a plurality of spaces each of which being arranged between two of said teeth. Said plurality of teeth includes at least one first gearshifting tooth and at least one second tooth arranged immediately downstream of said at least one first gearshifting tooth with reference to a rotation direction (R) of the sprocket during pedaling. Said plurality of spaces includes at least one first space defined between said at least one first gearshifting tooth and said at least one second tooth and having a predetermined circumferential extension and at least one second space arranged downstream of said at least one second tooth with reference to said rotation direction (R) and having a circumferential extension greater than that of said at least one first space.